Method for producing lubricating base oil with low cloud point and high viscosity index

ABSTRACT

The present invention relates to a method for producing lubricating base oil with a low cloud point and a high viscosity index. In the method, a lubricating base oil with a low pour point, a low cloud point and a high viscosity index is produced by a hydrorefining-isomerization/asymmetrical cracking-hydrofinishing in the presence of hydrogen, wherein a highly waxy heavy fraction oil having an initial boiling point of 300° C. to 460° C., a wax content of 5% or more, a pour point of −20° C. or more and a cloud point of −5° C. or more is used as a raw material, and naphtha and middle fraction oil being co-produced. The method is characterized mainly in the high yield of heavy base oil, a low pour point and cloud point, a high viscosity and viscosity index of the base oil.

FIELD OF THE INVENTION

The present invention relates to a method for producing a lubricatingbase oil with a low cloud point (<−5° C.) and a high viscosity index(>120).

BACKGROUND OF THE INVENTION

Patent CN101134910A discloses a method for lowering the pour point andthe cloud point of a lubricating oil distillate. In the method, acatalytic dewaxing process is adopted, and the catalyst includes nickelmetal as an active component, which is contained in a support of a ZSM-5molecular sieve. The pour point of a light deasphalted hydrotreated oilcan be lowered from 9° C. to −24° C., and the cloud point can be loweredfrom 12° C. to −16° C. The method has the following obviousdisadvantage: the yield and the viscosity of the base oil product willbe greatly decreased when the wax content in the feed stock is high, andthe drops of the pour point and the cloud point need to be increased.

Patent CN1524929 discloses a method for lowering the cloud point of alubricating base oil, in which a lube stock is first subjected tosolvent pre-dewaxing, the pour point of the dewaxed oil is −5° C. to 15°C.; the pre-dewaxed oil is subjected to hydrotreating to reduce thesulfur content and the nitrogen content; the pre-dewaxed oil afterhydrotreating is subjected to isodewaxing, to obtain a lubricating baseoil with a low cloud point. In order to avoid increase of the severityof the reaction and a resulted severe cracking reaction, in the method,most of the wax needs to be removed through a solvent pre-dewaxingprocess, and then a hydrotreating and isodewaxing process is performed.The pour point of the dewaxed oil of the method should be not higherthan 15° C., otherwise the cloud point of the isomerization productcannot be lowered to less than 0° C., even cannot be lowered to lessthan 5° C.

U.S. Pat. No. 6,699,385 discloses a method for lowering the cloud pointthrough an isodewaxing process. In order to avoid increase of theseverity of the reaction and a resulted severe cracking reaction, thewaxy feed stock needs to be first fractionated, and a light fraction issubjected to isodewaxing, and the cloud point can only be decreased toabout 0° C.

All the methods for dewaxing a lubricating base oil disclosed in thepublished patents and documents above do not clarify or imply a methodfor producing a base oil with a low pour point, a low cloud point and ahigh viscosity index by an isomerization-asymmetrical cracking reactionprocess, and compared with the method disclosed in the published patentsand documents, the yield of a base oil, especially the yield of a heavybase oil of an isomerization-symmetric cracking reaction process ishigher.

SUMMARY OF THE INVENTION

The present invention is directed to a method for producing alubricating base oil having a low cloud point (<−5° C.) and a highviscosity index (>120), wherein a highly waxy heavy fraction oil havingan initial boiling point of 300° C. to 460° C., a wax content of 5% ormore, a pour point of −20° C. or more and a cloud point of −5° C. ormore is used as raw material to produce a API (American PetroleumInstitute) II, III (see the classification standard in Table 1) typelubricating base oil having a low pour point and a high viscosity indexby a hydrogenation pre-refining-isomerization/asymmetricalcracking-supplementary refining three-stage hydrogenation process.

The production method provided by the present invention includes: (1) ahydrorefining process: at a certain hydrogen pressure, a waxy feed stockcontacts a hydrorefining catalyst and is subjected to desulfurization,denitrogenation, aromatic saturation and an ring-opening reaction,products of the hydrorefining reaction are separated by a strippingcolumn, and the bottom fraction enters a hydroisomerization/asymmetricalcracking process; (2) a hydroisomerization/asymmetrical crackingprocess: at a certain hydrogen pressure, a bottom product of thestripping column contacts an isomerization-asymmetrical crackingcatalyst and is subjected to isomerization-asymmetrical cracking and ahydrogenation saturation reaction, to obtain a product having a low pourpoint, a low cloud point, a low aromatic content and a high viscosityindex, and then all the product directly enters a hydrofinishingprocess; (3) a hydrofinishing process: at a certain hydrogen pressure,the isomerization-asymmetrical cracking reaction product contacts ahydrofinishing catalyst and is subjected to a hydrogenation saturationreaction, to obtain a hydrofinishing oil having good light stability andthermal stability; and (4) a product separation process: the productobtained in the hydrofinishing process is separated into a gas phaseproduct and a liquid phase product by a hot high-pressure separator anda cold low-pressure separator, the liquid product passes through anormal-pressure fractionating column and a reduced-pressurefractionating column to extract naphtha, kerosene, diesel oil and light,middle and heavy lubricating base oil having a low pour point and a highviscosity index.

According to the method of the present invention, the feed stockincludes anyone of furfural refined oil, foots oil, cerate (soft wax),propane deasphalted oil (DAO), hydrocracking unconverted oil (UCO),Fischer-Tropsch wax, vacuum gas oil and other waxy oils or a mixturethereof.

According to the method of the present invention, the hydrorefiningcatalyst includes 60 wt % to 90 wt % of one or more of alumina, silicaand titania, and 10 wt % to 40 wt % of one or more of molybdenumtrioxide, tungsten trioxide, nickel oxide and cobalt oxide.

According to the method of the present invention, before use, thehydrorefining catalyst is pre-sulfurated by hydrogen sulfide orsulfur-containing feed stock at a temperature of 150 to 350° C. in thepresence of hydrogen. This type of pre-vulcanization may be carried outex situ or in situ.

According to the method of the present invention, the hydrorefiningprocess conditions are: reaction temperature: 350° C. to 410° C.,hydrogen partial pressure: 10 MPa to 18 MPa, space velocity (LHSV): 0.5h⁻¹ to 2.0 h⁻¹, and volume ratio of hydrogen to oil:300 Nm³/m³ to 1000Nm³/m³.

According to the method of the present invention, the oil obtained bystripping separation of the hydrorefining product has a total sulfurcontent of no higher than 10 μg/g and a total nitrogen content of nohigher than 5 μg/g.

According to the method of the present invention, theisomerization-asymmetrical cracking catalyst is at least one of thefollowing one-dimensional 10-membered ring mesoporous compositemolecular sieves: a ZSM-22/ZSM-23 composite molecular sieve, aZSM-23/ZSM-22 composite molecular sieve, a ZSM-5/SAPO-11 compositemolecular sieve, a ZSM-22/SAPO-11 composite molecular sieve, aZSM-23/SAPO-11 composite molecular sieve, an EU-1/SAPO-11 compositemolecular sieve, and a NU-87/SAPO-11 composite molecular sieve. Thecontent of the molecular sieve is 40% to 80%, and the rest is aluminaand at least one group VIII noble metal, where the noble metal is Ptand/or Pd and has a content of 0.3 wt % to 0.6 wt %. The average porediameter of the catalyst is 0.3 nm to 0.8 nm, the average pore volume is0.1 ml/g to 0.4 mug, and the BET specific surface area is 120 m²/g to300 m²/g.

According to the method of the present invention, before use, theisomerization/asymmetrical cracking catalyst needs to be pre-reduced ata temperature of 150 to 450° C. in the presence of hydrogen.

According to the method of the present invention, theisomerization/asymmetrical cracking process conditions are: reactiontemperature: 260° C. to 410° C., hydrogen partial pressure: 10 MPa to 18MPa, volume space velocity: 0.5 h⁻¹ to 3.0 h⁻¹, volume ratio of hydrogento oil:300 Nm³/m³ to 1000 Nm³/m³.

According to the method of the present invention, the hydrofinishingcatalyst includes amorphous silica-alumina and at least one group VIIInoble metal.

According to the method of the present invention, the hydrofinishingcatalyst has a ratio of SiO₂:Al₂O₃ of 1:1 to 9, an average pore radiusof 1.0 nm to 5.0 nm, a pore volume of 0.3 ml/g to 1.0 ml/g, and a BETspecific surface area of 260 m²/g to 450 m²/g. The noble metal is Ptand/or Pd, and the content of the noble metal is 0.3 wt % to 0.6 wt %.

According to the method of the present invention, before use, thehydrofinishing catalyst is generally pre-reduced at a temperature of150° C. to 450° C. in the presence of hydrogen.

According to the method of the present invention, the hydrofinishingreaction conditions are: reaction temperature: 180° C. to 320° C.,hydrogen partial pressure: 10 MPa to 18 MPa, volume space velocity: 0.5h⁻¹ to 3.0 h⁻¹, volume ratio of hydrogen to oil:300 Nm³/m³ to 1000Nm³/m³.

According to the method of the present invention, the normal-pressuredistillation and reduced-pressure distillation process are to separatethe oil mixture after supplementary refining by normal-pressuredistillation and reduced-pressure distillation, to obtain a naphtha, amiddle fraction oil and a lubricating base oil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows product distribution of Example 1 and Comparative Example1.

FIG. 2 shows product distribution of Example 2 and Comparative Example2.

FIG. 3 is a flowchart of an isomerization-asymmetricalcracking/supplementary refining process of a lubricating base oil.

FIG. 4 is a flowchart of a hydrorefining/isodewaxing/hydrofinishingprocess of a lubricating base oil.

FIG. 5 is a flowchart of a hydrorefining/isomerization-asymmetricalcracking/hydrofinishing process of a lubricating base oil.

FIG. 6 is a flowchart of an isomerization-asymmetricalcracking/hydrofinishing process of a lubricating base oil.

PREFERRED EMBODIMENTS Examples

The present invention is further described with the following examples.

The hydrorefining catalyst and the supplementary refining catalyst usedin the examples of the present invention and preparation method thereofare briefly described as follows:

Same hydrorefining catalyst and hydrofinishing catalyst are used in theexamples and comparative examples of the present invention. Thehydrorefining catalyst is prepared according to the following process:pseudo-boehmite having an appropriate pore structure is selected andused to prepare a strip-like support having a clover-shaped crosssection, after the support is dried and baked, Ni element and Mo elementare loaded on the alumina support by an impregnation method, and thendried and baked to obtain a hydrorefining catalyst, wherein the NiOcontent is 4.20%, the MoO₃ content is 18.3%, and the rest is alumina,the specific surface area is 175 m²/g, and the pore volume is 0.45cm³/g.

The isomerization/asymmetrical cracking catalyst used in the examples isa 0.5% Pt/ZSM-22/SAPO-11 catalyst prepared according to the methoddescribed in Example 12 of patent CN 1762594A.

In a method for preparing the hydrofinishing catalyst, amorphoussilica-alumina used as support is prepared by using cocurrent flow fixedpH value and silica-alumina coprecipitation. After being dried andbaked, the support is squeezed into a strip having a clover-shaped crosssection, and dried and baked, and then metal Pt is loaded by animpregnation method, and then dried and baked to obtain a hydrofinishingcatalyst, wherein the Pt content is 0.51%, the rest is silica andalumina, the ratio of SiO₂:Al₂O₃ is 1:6.3, the specific surface area is305 cm²/g, and the pore volume is 1.08 cm³/g.

Comparative Example 1

A SAPO-11 molecular sieve was synthesized by a method described inExample 18 of U.S. Pat. No. 4,440,871. Pseudo-boehmite is incorporatedinto a SAPO-11 molecular sieve powder in a ratio of 70% SAPO-11molecular sieve to 30% pseudo-boehmite, and then a small amount of anadhesive such as an aqueous solution of HNO₃ was added, blended andshaped into a strip of φ1.2 mm, baked at 110° C. for 24 hours and at600° C. for 24 hours, and pulverized into particles having a length of 1mm to 2 mm. A sufficient amount of support particles was impregnated ina suitable amount of a Pt(NH₃)₄Cl₂ solution having a concentration of 3%for 16 hours by a common pore filling impregnation method, and thendried at 120° C. for 4 hours and baked at 480° C. for 8 hours. 200 ml ofthe prepared catalyst was pre-reduced by pure hydrogen in situ on ahigh-pressure hydrogenation reaction experimental device having acatalyst load of 200 ml to obtain a 0.5% Pt/SAPO-11 catalyst. Theisodewaxing catalyst reduction conditions are: hydrogen flow rate: 2000mL/h, the temperature was raised to 250° C. at a rate of 5° C./min andmaintained at 250° C. for 2 hours. Then, the temperature was raised to450° C. at a rate of 5° C./min and maintained at 450° C. for 2 hours,and the reaction temperature was adjusted in a hydrogen flow. Thehydrogenation pre-refining-isodewaxing-hydrofinishing process shown inFIG. 4 and the process conditions shown in Table 3 were adopted,paraffin base 650N furfural refined oil was used as a raw material, ofwhich the physical and chemical properties are shown in Table 2. Thehydrorefining catalyst and the supplementary refining catalyst were thesame as the catalysts used in the examples mentioned above.

Example 1

According to the process shown in FIG. 4, the experimental device andthe feed stock were the same as those in Comparative Example 1. Theother reaction conditions were the same as those in Comparative Example1 except that the reaction temperature of isomerization/asymmetricalcracking was 351° C., and the space velocity was 0.75 h⁻¹. The reactionconditions of Comparative Example 1 are shown in Table 3.

Product distribution comparison of Example 1 and Comparative Example 1is shown in Table 4, and main product properties are shown in Table 5.

According to the process shown in FIG. 4, paraffin base 200SN lightlydewaxed oil was used as a feed stock in the experimental device ofComparative Example 1, and the physical and chemical properties of thefeed stock are shown in Table 2. The reaction conditions are shown inTable 3.

TABLE 2 Properties of feed stocks of Comparative Example 1 and Example 1650SN Analysis Item Furfural Refined Oil Method 20° C. Density, g/cm³0.8721 GB/T 1884 Kinematic Viscosity 10.16 GB/T 265 (100° C.), mm²/sKinematic Viscosity — GB/T 265 (40° C.), mm²/s Viscosity Index — GB/T1995 Pour Point, ° C. 60 GB/T 3535 Cloud Point, ° C. >60 GB/T 6986-86Sulfur Content, μg/g 607 ASTM D2622 Nitrogen Content, μg/g 322 ASTMD5762 Composition, % SH/T0753 Saturated Hydrocarbons 86.08 AromaticHydrocarbons 13.58 Colloid + Asphaltene 0.34 Distillation Range, ° C. HK421 ASTM D2887  5% 477 10% 498 30% 516 50% 525 70% 533 90% 541 95% 550KK 557

TABLE 3 Reaction conditions adopted in Comparative Example 1 and Example1 Hydrorefining Isomerization Hydrofinishing Comparative ComparativeComparative Example 1 Example 1 Example 1 Example 1 Example 1 Example 1Average 370 370 378 351 230 230 Temperature, ° C. Hydrogen 13 13 12 1212 12 Partial Pressure, MPa Liquid hourly 0.90 1.00 0.70 0.75 1.50 1.50Volume Space Velocity, h⁻¹ Raito of 500 500 500 500 500 500 Hydrogen toOil, Nm³/m³

TABLE 4 Product distribution of Comparative Example 1 and Example 1Yield, % Product Example 1 Comparative Example 1 Fuel Gas + Naphtha19.96 15.71 Diesel Oil 2.96 11.58 2 cst Base Oil 3.78 24.86 5 cst BaseOil 0 4.49 10 cst Base Oil 73.30 47.85 Total Base Oil Yield 77.08 72.71

TABLE 5 Properties of heavy base oil products of Comparative Example 1and Example 1 Comparative Analysis Analysis Item Example 1 Example 1Method Initial Boiling Point, ° C. 421 385 GB/T 9168 20° C. Density,g/cm³ 0.8424 0.8524 GB/T 1884 Pour Point, ° C. −15 −15 GB/T 3535 CloudPoint, ° C. 5 −6 GB/T 6986-86 Aromatic Content, % 1.2 0 Open FlashPoint, ° C. 265 270 GB/T 3536 Chroma, number +30 +30 GB/T 3555 KinematicViscosity 60.89 61.06 GB/T 265 (40° C.), mm²/s Kinematic Viscosity 9.3139.423 GB/T 265 (100° C.), mm²/s Viscosity Index 132 136 GB/T 1995

It can be seen from Tables 2 to 5 and FIG. 1 that, the pour point of thefeed stock used in the hydrorefining, isomerization-asymmetricalcracking, hydrofinishing process in Example 1 is up to 60° C.,indicating that the feed stock contains a large amount ofhigh-carbon-number wax molecules. In the method of Example 1 andComparative Example 1, the hydrocracking reaction occurs simultaneouslywith isomerization. However, different from the conventionalhydrocracking reaction of Comparative Example 1, Example 1 hassignificant features of an asymmetrical cracking reaction, that is, thecleavage of a C—C bond preferably occurs at a position close to two endsof a long-chain paraffin, so that the yields of both small-moleculeproducts (gas and naphtha) and big-molecule products (10 cst base oil)are high, and are up to 19.96% and 73.3%, respectively, while the yieldsof diesel oil and light base oil (2 cst base oil) are only 2.96% and3.78% respectively. The cracking reaction in the method of ComparativeExample 1 occurs at a position close to the center of a long-chainparaffin, so that the yields of both small-molecule products(gas+naphtha) and big-molecule products (10 cst base oil) are 15.71% and47.85% respectively, which are both lower than those in Example 1, andthe yields of diesel oil and light base oil (2 cst base oil) are 11.58%and 24.86% respectively, which are both higher than those in Example 1.At the same time, the cloud point of the heavy base oil product ofExample 1 is 11° C. lower than that of the heavy base oil product ofComparative Example 1. The viscosity index of the heavy base oil productof Example 1 is higher than that of the heavy base oil product ofComparative Example 1 by 4%.

Comparative Example 2

A ZSM-22 molecular sieve was synthesized by the method described inExample 2 of U.S. Pat. No. 5,783,168. Pseudo-boehmite is incorporatedinto a ZSM-22 molecular sieve powder in a ratio of 70% ZSM-22 molecularsieve to 30% pseudo-boehmite, and then a small amount of an adhesivesuch as an aqueous solution of HNO₃ was added, blended and shaped into astrip of φ1.2 mm, baked at 110° C. for 24 hours and at 600° C. for 24hours, and breaked into particles having a length of 1 mm to 2 mm. Asufficient amount of support particles was impregnated in a suitableamount of a Pt(NH₃)₄Cl₂ solution having a concentration of 3% for 16hours by a common pore filling impregnation method, and then dried at120° C. for 4 hours and baked at 480° C. for 8 hours. 200 ml of theprepared catalyst was pre-reduced by pure hydrogen in situ in ahigh-pressure hydrogenation reaction experimental device having acatalyst load of 200 ml to obtain 0.5% of Pt/ZSM-22. The catalystreduction conditions were the same as those in Comparative Example 1. Aparaffin base 200SN dewaxed oil was used as a raw material, the physicaland chemical properties thereof are shown in Table 6, and ahydrorefining-isodewaxing-hydrofinishing series process (shown in FIG.4) and process conditions shown in Table 7 were adopted.

Example 2

The process, experimental device and feed stock were the same as thosein Comparative Example 2. The other reaction conditions were the same asthose in Comparative Example 2 except that the temperature of theisomerization/asymmetrical cracking reaction was 325° C., and the liquidhourly space velocity was 1.2 h⁻¹.

The product distributions of the reactions of Example 2 and ComparativeExample 2 are shown in Table 8, and main properties of the products areshown in Table 9.

It can be seen from Tables 6 to 9 and FIG. 2 that compared withComparative Example 2, the method of Example 2 has significant featuresof a hydrorefining-isomerization/asymmetrical cracking-hydrofinishing,that is, the yield of a heavy base oil (5 cst base oil) is high, and theyields of small-molecule products (gas and naphtha) and big-moleculeproducts (10 cst base oil) are both high, and are up to 19.96% and 73.3%respectively, the yields of diesel oil and a light base oil (2 cst baseoil) are merely 2.96% and 3.78% respectively. The product distributionis in a bimodal distribution. At the same time, it can be seen that, thecloud point of the heavy base oil product of Example 2 is 10° C. lowerthan that of the heavy base oil product of Comparative Example 2.

TABLE 6 Feed stock properties 200SN Analysis Item Lightly Dewaxed OilStandard 20° C. Density, g/cm³ 0.8797 GB/T 1884 Kinematic Viscosity6.277 GB/T 265 (100° C.), mm²/s Kinematic Viscosity 40.34 GB/T 265 (40°C.), mm²/s Viscosity Index 103 GB/T 1995 Pour Point, ° C. −3 GB/T 3535Cloud Point, ° C. 15 GB/T 6986-86 Sulfur Content, μg/g 420 ASTM D2622Nitrogen Content, μg/g 144 ASTM D5762 Composition, % SH/T0753 SaturatedHydrocarbons 88.23 Aromatic Hydrocarbons 11.44 Colloid + Asphaltene 0.33Distillation Range, ° C. HK 373 ASTM D2887  5% 404 10% 414 30% 429 50%441 70% 453 90% 478 95% 487 KK 491

TABLE 7 Reaction conditions of Comparative Examples 1 and 2Hydrorefining Isomerization Hydrofinishing Comparative ComparativeComparative Example 2 Example 2 Example 2 Example 2 Example 2 Example 2Average 368 368 360 325 230 230 Temperature, ° C. Hydrogen 13 13 12 1212 12 Partial Pressure, MPa Liquid hourly 1.0 1.0 0.9 1.2 1.5 1.5 VolumeSpace Velocity, h⁻¹ Raito of 500 500 500 500 500 500 Hydrogen to Oil,Nm³/m³

TABLE 8 Product distribution of Examples 1 and 2 and ComparativeExamples 1 and 2 Yield, % Product Comparative Example 2 Example 2 Gas +Naphtha 8.85 9.74 Diesel 8.09 2.44 2 cst Base Oil 18.35 5.14 5 cst BaseOil 67.71 82.68 Total Base Oil Yield 86.06 88.82

TABLE 9 Properties of heavy base oil products of Comparative Example 2and Example 2 Comparative Analysis Analysis Item Example 2 Example 2Method Initial Boiling Point, ° C. 400 394 GB/T 9168 20° C. Density,g/cm³ 0.8521 0.8629 GB/T 1884 Pour Point, ° C. −18 −21 GB/T 3535 CloudPoint, ° C. −5 −15 GB/T 6986-86 Open Flash Point, ° C. 220 235 GB/T 3536Chroma, number +30 +30 GB/T 3555 Kinematic Viscosity 34.56 39.39 GB/T265 (40° C.), mm²/s Kinematic Viscosity, 5.713 6.273 GB/T 265 (100° C.),mm²/s Viscosity Index 104 105 GB/T 1995

Example 3

According to the process shown in FIG. 4, the experimental device is thesame as that in Comparative Example 1, and the feed stock is a 100Ncerate obtained from crude oil by processes of reduced-pressuredistillation, furfural refining and acetone-toluene dewaxing, of whichthe physical and chemical properties are shown in Table 10. Under theprocess conditions shown in Table 11, the resulting product distributionis shown in Table 12, and the main properties of the products are shownin Table 13.

Example 4

According to the process shown in FIG. 4, the experimental device is thesame as that in Comparative Example 1, and the feed stock is a 400Ncerate shown in Table 10. Under the process conditions shown in Table11, the resulting product distribution is shown in Table 12, and themain properties of the products are shown in Table 13.

It can be seen from Tables 10 to 13 that the distribution of the productof the isomerization/asymmetrical cracking in Example 3 is similar tothose of the products of isomerization/asymmetrical cracking in Examples1 and 2, the product mainly includes light component products (gas andnaphtha) and a 2 cst base oil product, and the yields of the twoproducts are 17.32% and 70.83% respectively, and the diesel yield is11.87%, indicating a bimodal distribution of a high yield of the lightcomponent product and the heavy component product and a low yield of themiddle fraction. The product distribution in Example 4 is similar tothat in Example 3, and the feature of bimodal distribution is moresignificant. The pour points and the cloud points of the 2 cst and 6 cstbase oil products of Examples 3 and 4 are very low, and the viscosityindex of the 6 cst base oil is up to 123, which meets the requirementsof API Group III base oil.

TABLE 10 Properties of feed stocks of Examples 3 and 4 Analysis Item100N Cerate 400N Cerate Density (20° C.), g/cm³ 0.8319 0.8643 KinematicViscosity (40° C.), mm²/s 8.292 41.77 Kinematic Viscosity (100° C.),mm²/s 2.476 7.205 Viscosity Index 128 136 Pour Point, ° C. 27 33 SulfurContent, μg/g 490 534 Nitrogen Content, μg/g 176 430 Composition, %Saturated Hydrocarbons 90.11 83.51 Aromatic Hydrocarbons 9.17 15.35Polar Compounds 0.72 1.14 Distillation Range, ° C. HK 307 370  5% 342422 10% 348 450 30% 358 469 50% 367 477 70% 376 486 90% 386 498 95% 392505 KK 404 510

TABLE 11 Process conditions of Examples 3 and 4 Isomerization-Asymmetrical Process Hydrorefining Cracking Hydrofinishing ConditionsExample 3 Example 4 Example 3 Example 4 Example 3 Example 4 Average 365370 320 360 230 230 Temperature, ° C. Hydrogen 13.0 13.0 12.0 12.0 12.012.0 Partial Pressure, MPa Volume 1.0 1.0 0.8 0.5 1.33 0.83 SpaceVelocity, h⁻¹ Raito of 350 560 350 560 350 560 Hydrogen to Oil, Nm³/Nm³

TABLE 12 Product distributions of Examples 3 and 4 Yield, % ProductExample 3 Example 4 Gas + Naphtha 17.32 16.54 Diesel 11.87  5.81 2 cstBase Oil 70.81 — 6 cst Base Oil — 77.65 10 cst Base Oil  — — Total BaseOil Yield 70.81 77.65

TABLE 13 Properties of base oil products of Examples 3 and 4 Feed stock100N Cerate 400N Cerate Analysis Product 2 cst base oil 6 cst base oilMethod Density (20° C.), 0.8340 0.8504 GB/T 1884 g/cm³ Pour Point, ° C.−25 −30 GB/T 3535 Cloud Point, ° C. −15 −19 GB/T 6986-86 Open FlashPoint, ° C. 176 214 GB/T 3536 Chroma, number +30 +30 GB/T 3555 KinematicViscosity 9.520 35.34 GB/T 265 (40° C.), mm²/s Kinematic Viscosity 2.5886.168 GB/T 265 (100° C.), mm²/s Viscosity Index 102 123 GB/T 1995

Example 5

According to the process shown in FIG. 4, the experimental device is thesame as that in Comparative Example 1, and the feed stock is a 650Ncerate shown in Table 9, which is a waxy oil obtained from crude oil byprocesses of reduced-pressure distillation, furfural refining andacetone-toluene dewaxing, and the physical and chemical properties.Under the process conditions shown in Table 14, the resulting productdistribution is shown in Table 15, and the main properties of theproducts are shown in Table 16.

Example 6

According to the process shown in FIG. 4, the experimental device is thesame as that in Comparative Example 1, and the feed stock is a 150BScerate, which is a waxy oil obtained from paraffin-based crude oil byprocesses of reduced-pressure distillation, propane deasphalting,furfural refining and acetone—toluene dewaxing, and the physical andchemical properties thereof are shown in Table 14. Under the processconditions shown in Table 15, the resulting product distribution isshown in Table 16, and the main properties of the products are shown inTable 17.

It can be seen from Tables 14 to 17 that the fractions of 650SN cerateand 150BS cerate are very heavy, and the pour points thereof are veryhigh. With regard to the two types of heavy and waxy feed stocks, thereduction of the pour point of the base oil needs to be up to 78° C. toachieve a pour point of base oil of no higher than −15° C. The featuresof high yields of small-molecule products (gas and naphtha) andbig-molecule products (8 cst and 20 cst base oils) generated by thehydrorefining-isomerization/asymmetrical cracking-hydrofinishing and lowyield of the middle fraction oil (diesel +2 cst base oil) aresignificant. The viscosity index of the heavy product having a low pourpoint is extremely high, which can be up to 140, and the pour point andthe cloud point of the heavy product can be decreased to a very lowlevel.

TABLE 14 Properties of feed stocks of Examples 5 and 6 650N 150BSAnalysis Analysis Item Cerate Cerate Standard Kinematic Density (20°C.), 0.8646 0.8710 GB/T 1884 g/cm³ Kinematic Viscosity (40° C.), — —GB/T 265 mm²/s Kinematic Viscosity (100° C.), 9.359 25.10 GB/T 265 mm²/sPour Point, ° C. 63 57 GB/T 3535 Sulfur Content, μg/g 690 752 ASTM D2622Nitrogen Content, μg/g 517 674 ASTM D5762 Composition, % SH/T0753Saturated Hydrocarbons 87.65 69.1 Aromatic Hydrocarbons 11.31 23.0 Polarcompounds 1.04 7.9 Simulated Distillation, ° C. HK 380 410 ASTM D2887 5% 480 465 10% 505 507 30% 522 562 50% 540 609 70% 551 667 90% 565 —95% 569 — KK 589 —

TABLE 15 Process conditions of Examples 5 and 6 Isomerization-Asymmetrical Reaction Hydrorefining Cracking Hydrofinishing ConditionsExample 5 Example 6 Example 5 Example 6 Example 5 Example 6 Average 370370 350 375 230 230 Temperature, ° C. Hydrogen 14.5 14.5 14.0 14.0 14.014.0 Partial Pressure, MPa Liquid hourly 0.75 0.75 0.5 0.5 1.25 1.25Volume Space Velocity, h⁻¹ Raito of 750 750 750 750 750 750 Hydrogen toOil, Nm³/Nm³

TABLE 16 Product distributions of Examples 5 and 6 Yield, % ProductExample 5 Example 6 Fuel Gas + Naphtha 19.31 18.76 Diesel  4.03  2.13 2cst Base Oil  8.77  3.43 6 cst Base Oil — 14.77 8 cst Base Oil 67.89 —20 cst base oil  — 60.91 Total Base Oil Yield 76.66 79.11

TABLE 17 Properties of heavy base oil products of Examples 5 and 6 Feedstock 650N Cerate 150BS Cerate Analysis Product Properties 10 cst baseoil 20 cst base oil Method Density (20° C.), 0.8495 0.8542 GB/T 1884g/cm³ Pour Point, ° C. −19 −18 GB/T 3535 Cloud Point, ° C. −8 −6 GB/T6986-86 Open Flash Point, ° C. 268 293 GB/T 3536 Chroma, number +30 +30GB/T 3555 Kinematic Viscosity 45.17 151.1 GB/T 265 (40° C.), mm²/sKinematic Viscosity 8.050 19.08 GB/T 265 (100° C.), mm²/s ViscosityIndex 152 144 GB/T 1995

Example 7

A hydrocracking UCO is a heavy fraction oil generated from areduced-pressure fraction oil by a hydrorefining-hydrocracking reaction,the impurities such as sulfur and nitrogen have been removed, and mostof the aromatic hydrocarbons have been subjected to hydrosaturation andring-opening, such that the hydrocracking UCO needs not to be subjectedto a hydrorefining reaction to remove sulfur and nitrogen, and needs notto be subjected to a hydrorefining-reaction to improve the viscosityindex, and the isomerization-asymmetrical cracking/hydrofinishing shownin FIG. 6 can be adopted. Hydrogenation evaluation was performed on theexperimental device, and a hydrocracking UCO having the physical andchemical properties shown in Table 18 was uses as a feed stock. Underthe process conditions shown in Table 19, the resulting productdistribution is shown in Table 20, and main properties of the productare shown in Table 21. It can be seen from Tables 18 to 21 that thehydrocracking UCO has a low sulfur content and nitrogen content, and ahigh viscosity index and pour point. After an isomerization-asymmetricalcracking/hydrofinishing with mild process conditions, the productdistribution has features of high yields of small-molecule products (gasand naphtha) and big-molecule products (8 cst and 20 cst base oils) andlow yield of the middle fraction oil (diesel +2 cst base oil), and thecloud point of the product achieves −15° C.

TABLE 18 Properties of the feed stock of Example 7 Analysis ItemHydrocracking UCO Analysis Standard Kinematic Density (20° C.), 0.8245GB/T 1884 g/cm³ Kinematic Viscosity (40° C.), 15.74 GB/T 265 mm²/sKinematic Viscosity (100° C.), 3.824 GB/T 265 mm²/s Viscosity Index 139GB/T 1995 Pour Point, ° C. 33 GB/T 3535 Sulfur Content, μg/g 2.787 ASTMD2622 Nitrogen Content, μg/g 1.778 ASTM D5762 Composition, % SH/T0753Saturated Hydrocarbons 98.75 Aromatic Hydrocarbons 1.11 Polar Compounds0.14 Distillation Range, ° C. HK 331 ASTM D2887  5% 367 10% 375 30% 39250% 409 70% 433 90% 473 95% 491 KK 516

TABLE 19 Process conditions of Example 7 Isomerization- AsymmetricalProcess Conditions Cracking Hydrofinishing Average Temperature, ° C. 310230 Hydrogen Partial Pressure, 12.4 12.4 MPa Liquid Hourly Volume Space1.0 1.7 Velocity, h⁻¹ Raito of Hydrogen to Oil, Nm³/Nm³ 350 350

TABLE 20 Product distribution of Example 7 Product Product Yield, % FuelGas + Naphtha 15.9 Diesel 4.66 2 cst Base Oil 1.09 4 cst Base Oil 78.35Total Base Oil Yield 79.44

TABLE 21 Properties of the 4 cst base oil product of Example 7 AnalysisItem 4 cst Base Oil Analysis Method Density (20° C.), g/cm³ 0.8288 GB/T1884 Pour Point, ° C. −18 GB/T 3535 Cloud Point, ° C. −15 GB/T 6986-86Open Flash Point, ° C. 204 GB/T 3536 Chroma, number +30 GB/T 3555Kinematic Viscosity (40° C.), 17.58 GB/T 265 mm²/s Kinematic Viscosity(100° C.), 3.974 GB/T 265 mm²/s Viscosity Index 124 GB/T 1995

Example 8

An Fischer-Tropsch wax is a hydrocarbon product with high-carbon-numberlong-chain normal paraffins as the main component synthesized in thepresence of a Co-based catalyst. The wax mainly includes C₈ to C₄₅normal paraffins, and the distribution of maximum carbon number isaround C₁₈. After cutting off components distillated at less than 320°C., the distribution of maximum carbon number of the Fischer-Tropsch waxis slight shifted to a higher carbon number. FIG. 3 shows carbon numberdistribution of a product synthesized in the presence of a Co-basedcatalyst and an Fischer-Tropsch wax after cutting off componentsdistillated at less than 320° C. by atmospheric distillation. TheFischer-Tropsch wax substantially does not contain impurities such assulfur and nitrogen and aromatic hydrocarbons, and needs not to besubjected to a hydrorefining reaction to remove sulfur and nitrogen, andneeds not to be subjected to a hydrorefining reaction to improve theviscosity index, and can be directly subjected to anisomerization-asymmetrical cracking/hydrofinishing shown in FIG. 6. Theexperimental device of isodewaxing is the same as that in ComparativeExample 1, the components distillated at more than 320° C. in theFischer-Tropsch wax was used as a feed stock, of which the physical andchemical properties are shown in Table 22. Under the process conditionsshown in Table 23, the resulting product distribution is shown in Table24, and main properties of the product are shown in Table 25. It can beseen from Tables 22 to 25 that, the distribution of the product afterthe isomerization-asymmetrical cracking/hydrofinishing has the featureof bimodal distribution. Meanwhile, the cloud point of the 2 cst baseoil product achieves −6° C., and the viscosity index is up to 162.

TABLE 18 Properties of the feed stock of Example 8 Analysis ItemFischer-Tropsch wax Analysis Standard 20° C. Density, g/cm³ 0.8536 GB/T1884 100° C. Viscosity, mm²/s 4.673 GB/T 265 Pour Point, ° C. 59 GB/T3535 Sulfur Content, μg/g Not detected ASTM D2622 Nitrogen Content, μg/gNot detected ASTM D5762 Distillation Range, ° C. HK 316 ASTM D2887  5%366 10% 375 30% 397 50% 409 70% 425 90% 495 95% 531 KK 549

TABLE 18 Process conditions of Example 8 Isomerization- AsymmetricalSupplementary Process Condition Cracking Refining Average Temperature, °C. 360 230 Hydrogen Partial Pressure, 12.4 12.4 MPa Volume SpaceVelocity, h⁻¹ 0.5 0.85 Raito of Hydrogen to Oil, Nm³/Nm³ 750 750

TABLE 19 Product distribution of Example 8 Product Product Yield, % FuelGas + Naphtha 23.7 Diesel 6.63 2 cst Base Oil Yield 69.67

TABLE 20 Properties of the product of Example 8 Product 2 cst Base OilAnalysis Method 20° C. Density, g/cm³ 0.8416 GB/T 1884 Pour Point, ° C.−15 GB/T 3535 Cloud Point, ° C. −6 GB/T 6986-86 Open Flash Point, ° C.179 GB/T 3536 Chroma, number +30 GB/T 3555 40° C. Kinematic Viscosity,mm²/s 9.756 GB/T 265 100° C. Kinematic Viscosity, mm²/s 2.912 GB/T 265Viscosity Index 162 GB/T 1995

INDUSTRIAL APPLICABILITY

In the present invention, the highly waxy heavy fraction oil having aninitial boiling point of 300° C. to 460° C., a wax content of no lowerthan 5%, a pour point of no lower than −20° C., and a cloud point of nolower than −5° C. is used as a feed stock to produce a API (AmericanPetroleum Institute) Group II or Group III (see the classificationstandard in Table 1) type lubricating base oil having a low pour pointand a high viscosity index by a hydrorefining-isomerization/asymmetricalcracking-hydrofinishing three-stage hydrogenation process, wherein acritical reaction process of hydrogenation isomerization-asymmetricalcracking is involved. The isomerization/asymmetrical cracking reactioninclude two chemical reactions, namely, an isomerization reaction and anasymmetrical cracking reaction. When the isomerization is carried out,the linear paraffins having a high pour point and big-molecular andless-branched iso-paraffins with high pour point and high viscosityindex in the feed stock are subjected to an asymmetrical crackingreaction at the same time. The so-called asymmetrical cracking reactionrefers to a hydrocracking reaction occurs at a C—C bond close to the twoends of the paraffin, and a big-molecule and a small molecule aregenerated, wherein the small molecule belongs to the gas and naphthafraction, and the big-molecule belongs to the lubricating base oilfraction.

In the asymmetrical cracking reaction, a 10-membered ring compositemolecular sieve having a special pore structure is used as a catalystsupport to enhance the restriction of the catalyst pores on the internaldiffusion of normal paraffins and less-branched iso-paraffins, such thatthe cracking reaction preferably occurs at a position close to the twoends of the normal paraffins, thereby significantly improving the yieldof the base oil product, especially that of the heavy base oil product.

The isomerization/asymmetrical cracking reaction is characterized inthat the product has a bimodal distribution, that is, the yields of thelight components (gas and naphtha) and the heavy base oil having a lowpour point and a low cloud point are high, and the yield of a middlefraction oil (kerosene and diesel) is low. The method can solve theproblems of low yield of target product, high pour point and cloudpoint, high aromatic content and low viscosity index and the like in theproduction of lubricating base oil from heavy highly waxy oil byphysical processes such as solvent refining and solvent dewaxing and/orchemical processes such as hydrotreating, catalytic dewaxing,hydrotreating and hydrocracking. The process has the advantages of goodadaptability to heavy highly waxy feed stock, high yield of the heavybase oil product with good properties such as viscosity, viscosityindex, pour point and cloud point of the product and co-production ofnaphtha and a small amount of a middle fraction oil.

TABLE 1 API lubricating base oil Classification standard SaturatedHydrocarbon Class Content, % Sulfur Content, % Viscosity Index I <90and/or >0.03 80~120 II ≮90 ≯0.03 80~120 III ≮90 ≯0.03 >120 IVpoly-α-olefin (PAO) V Various base oils except I~IV

1. A method for producing a lubricating base oil with a low cloud pointand a high viscosity index, wherein the cloud point is lower than −5°C., and the viscosity index is higher than 120, the method comprises:producing a lubricating base oil by ahydrorefining-isomerization/asymmetrical cracking-hydrofinishing in thepresence of hydrogen, wherein a highly waxy heavy fraction oil having aninitial boiling point of 300° C. to 460° C., a wax content of 5% ormore, a pour point of −20° C. or more and a cloud point of −5° C. ormore is used as a raw material; (1) during the hydrorefining process, awax-containing heavy feed stock contacts a pre-refining catalyst, and issubjected to desulfurization, denitrogenation, aromatic saturation and aring-opening reaction, a light product generated in the hydrorefiningprocess is separated by a stripping column as a byproduct, and a heavyproduct enters an isomerization-asymmetrical cracking process; theoperating conditions of the hydrorefining process are: reactiontemperature: 350° C. to 410° C., hydrogen partial pressure: 10 MPa to 18MPa, space velocity: 0.5 h⁻¹ to 2.0 h⁻¹, volume ratio of hydrogen tooil:300 Nm³/m³ to 1000 Nm³/m³; the pre-refining catalyst comprises 60 wt% to 90 wt % of one or more of alumina, silica and titania, and 10 wt %to 40 wt % of one or more of molybdenum trioxide, tungsten trioxide,nickel oxide and cobalt oxide; (2) during the hydrogenationisomerization-asymmetrical cracking process, the heavy product generatedin the hydrorefining process contacts an isomerization-asymmetricalcracking catalyst, wax-containing component having a high pour point issubjected to an isomerization-asymmetrical cracking reaction, and isconverted into a an isomer and an asymmetrical cracking product having alow pour point, which then directly enters a hydrofinishing process; theoperating conditions of the hydrogenation isomerization-asymmetricalcracking process are: reaction temperature: 260° C. to 410° C., hydrogenpartial pressure: 10 MPa to 18 MPa, volume space velocity: 0.5 h⁻¹ to3.0 h⁻¹, volume ratio of hydrogen to oil:300 Nm³/m³ to 1000 Nm³/m³; thecatalyst: the content of mesoporous molecular sieve is 40% to 80%, thecontent of Pt and/or Pd is 0.3 wt % to 0.7 wt %, and alumina as thebalance; (3) during the hydrofinishing process, anisomerization-asymmetrical cracking reaction product having a low pourpoint contacts a hydrofinishing catalyst, residual aromatics and olefinsgenerated by the asymmetrical cracking reaction are hydrogenated andsaturated, and the resulting product is separated by a fractionatingcolumn to obtain a lubricating base oil and gaseous hydrocarbons,naphtha and middle fraction oil; the catalyst comprises amorphoussilica-alumina and at least one group VIII noble metal, the weight ratioof SiO₂:Al₂O₃ is 1:1˜9, the average pore size is 1.0 nm to 5.0 nm, thepore volume is 0.3 ml/g to 1.0 mug, the BET specific surface area is 260m²/g to 450 m²/g; the noble metal is Pt and/or Pd, and the content ofthe noble metal is 0.3 wt % to 0.6 wt %; and the hydrofinishing reactionconditions are: reaction temperature: 180° C. to 320° C., hydrogenpartial pressure: 10 MPa to 18 MPa, volume space velocity: 0.5 h⁻¹ to3.0 h⁻¹, volume ratio of hydrogen to oil:300 Nm³/m³ to 1000 Nm³/m³. 2.The method for producing a lubricating base oil with a low cloud pointof and a high viscosity index according to claim 1, wherein the heavyfeed stock comprises anyone of furfural refined oil, foots oil, cerate,propane deasphalted oil, hydrocracking UCO, vacuum gas oil andFischer-Tropsch wax or a mixture thereof.
 3. The method for producing alubricating base oil with a low cloud point of and a high viscosityindex according to claim 1, wherein the mesoporous molecular sieve usedin the hydrogenation isomerization-asymmetrical cracking reactioncatalyst is one of a ZSM-22/ZSM-23 composite molecular sieve, aZSM-23/ZSM-22 composite molecular sieve, a ZSM-22/SAPO-11 compositemolecular sieve, a ZSM-23/SAPO-11 composite molecular sieve, aZSM-5/SAPO-11 composite molecular sieve and an EU-1/SAPO-11 compositemolecular sieve.
 4. A method for producing a lubricating base oilcomprising: (1) contacting a wax-containing heavy feed stock with apre-refining catalyst and separating a light product from a heavyproduct; (2) contacting the heavy product with anisomerization-asymmetrical cracking catalyst wherein a wax-containingcomponent having a high pour point is subjected to anisomerization-asymmetrical cracking reaction, and is converted into anisomer and an asymmetrical cracking product having a low pour point; (3)contacting the isomer and the isomerization-asymmetrical crackingreaction product having a low pour point with a hydrofinishing catalystto generate a product; and (4) separating the product by a fractionatingcolumn to obtain a lubricating base oil and gaseous hydrocarbons,naphtha and middle fraction oil.
 5. The method of claim 4, wherein thelubricating base oil has a low cloud point and a high viscosity index.6. The method of claim 5, wherein the cloud point is lower than −5° C.,and the viscosity index is higher than
 120. 7. The method of claim 4,wherein the wax-containing heavy feed stock has an initial boiling pointof 300° C. to 460° C., a wax content of 5% or more, a pour point of −20°C. or more and a cloud point of −5° C.
 8. The method of claim 4, whereinthe contacting at step (1) subjects the wax-containing heavy feed stockto desulfurization, denitrogenation, aromatic saturation and aring-opening reaction.
 9. The method of claim 4, wherein operatingconditions of the contacting at step (1) comprise a reaction temperatureof from 350° C. to 410° C.; a hydrogen partial pressure of 10 MPa to 18MPa; a space velocity of from 0.5 h⁻¹ to 2.0 h⁻¹; and a volume ratio ofhydrogen to oil of from 300 Nm³/m³ to 1000 Nm³/m³.
 10. The method ofclaim 4, wherein the pre-refining catalyst comprises from 60 wt. % to 90wt. % of one or more of alumina, silica and titania; and 10 wt. % to 40wt. % of one or more of molybdenum trioxide, tungsten trioxide, nickeloxide and cobalt oxide.
 11. The method of claim 4, wherein thecontacting at step (2) subjects the heavy product is subjected to anisomerization-asymmetrical cracking reaction, and is converted into a anisomer and an asymmetrical cracking product having a low pour point. 12.The method of claim 4, wherein operating conditions of the contacting atstep (2) comprise a reaction temperature of from 260° C. to 410° C.; ahydrogen partial pressure of from 10 MPa to 18 MPa; a volume spacevelocity of from 0.5 h⁻¹ to 3.0 h⁻¹; and a volume ratio of hydrogen tooil of from 300 Nm³/m³ to 1000 Nm³/m³.
 13. The method of claim 4,wherein the isomerization-asymmetrical cracking catalyst comprises 40%to 80% mesoporous molecular sieve; a Pt and/or Pd content of 0.3 wt % to0.7 wt %; and alumina as the balance.
 14. The method of claim 13,wherein the mesoporous molecular sieve is at least one of aZSM-22/ZSM-23 composite molecular sieve, a ZSM-23/ZSM-22 compositemolecular sieve, a ZSM-22/SAPO-11 composite molecular sieve, aZSM-23/SAPO-11 composite molecular sieve, a ZSM-5/SAPO-11 compositemolecular sieve or an EU-1/SAPO-11 composite molecular sieve.
 15. Themethod of claim 4, wherein the contacting at step (3) hydrogenates andsaturates residual aromatics and olefins generated by the asymmetricalcracking reaction.
 16. The method of claim 4, wherein operatingconditions of the contacting at step (3) comprise a reaction temperatureof from 180° C. to 320° C.; a hydrogen partial pressure of from 10 MPato 18 MPa; a volume space velocity of from 0.5 h⁻¹ to 3.0 h⁻¹; and avolume ratio of hydrogen to oil of from 300 Nm³/m³ to 1000 Nm³/m³. 17.The method of claim 4, wherein the hydrofinishing catalyst comprisesamorphous silica (SiO₂)-alumina (Al₂O₃) and at least one group VIIInoble metal, wherein the weight ratio of SiO₂:Al₂O₃ is 1:1˜9; theaverage pore size is from 1.0 nm to 5.0 nm; the pore volume is from 0.3mL/g to 1.0 mL/g; the BET specific surface area is from 260 m²/g to 450m²/g; the noble metal is Pt and/or Pd; and the content of the noblemetal is from 0.3 wt % to 0.6 wt %.
 18. The method of claim 4, whereinthe isomer and an asymmetrical cracking product having a low pour pointdirectly enter the contacting at step (3).
 19. The method of claim 4,wherein the heavy feed stock comprises any one of furfural refined oil,foots oil, cerate, propane deasphalted oil, hydrocracking UCO, vacuumgas oil and Fischer-Tropsch wax or a mixture thereof.